Rostocker Meeresbiologische Beiträge Zur Fauna des Mittelmeeres Heft 18 7 The avifauna of Ibiza: an updated checklist including comments on abundances and ecology By Thomas Kellner, Mathias Krech, Axel Schulz & Carsten H. G. Müller Kellner T., Krech M., Schulz A. & C.H.G Müller (2007): The avifauna of Ibiza: an updated checklist including comments on abundances and ecology. Rostocker Meeresbiologische Beiträge 18: S. 7-29 Abstract. The Balearic Islands Menorca, Mallorca, Ibiza and Formentera are known to be of immense significance for European birds migrating to the South. They are used either as intermediate stops on the route to Africa or as the final winter destination. The Balearic bird communities also incorporate many permanent residents, however. The seasonal dynamics and the specific island situation have fascinated bird watchers for centuries. Continuing this tradition, the authors investigated the avifauna of Ibiza in the course of five excursions, carried out in the spring and fall of the years 1998-2001. Altogether, 110 bird species were identified audiovisually in various habitats around the coasts of Ibiza and the hilly landscape behind the coastline. The authors present a species list with comments on biology and ecology. Zoogeographical remarks are made regarding the spread of the Eurasian Collared Dove (Streptopelia decaocto). New data on the feeding ecology of three species are given: Barn Owl (Tyto alba), Long-eared Owl (Asio otus), and Woodchat Shrike (Lanius senator). Kurzfassung. Die Balearen Menorca, Mallorca, Ibiza and Formentera spielen eine wichtige Rolle für europäische Vögel auf dem Weg zu ihren Winterquartieren. Sie werden als Zwischenstation auf dem Weg nach Afrika genutzt oder zur auch selbst Überwinterung. Daneben gibt es viele Brutvögel. Der jahreszeitliche Wechsel und die Inselsituation haben Vogelbeobachter seit Jahrhunderten fasziniert. Die Autoren folgten dieser Tradition und erstellten im Verlauf von fünf Exkursionen nach Ibiza im Frühjahr und Herbst der Jahre 1998- 2001 eine kommentierte Artenliste mit Angaben zur Biologie und Ökologie. Insgesamt 110 Vogelarten wurden audiovisuell in Habitaten an der Küste und im anschließenden Hügelland identifiziert. Zoogeographische Überrlegungen erfolgen zur Ausbreitung der Türkentaube (Streptopelia decaocto). Es erfolgen neue Angaben zur Nahrungsökologie von Schleiereule (Tyto alba), Waldohreule (Asio otus) und Rotkopfwürger (Lanius senator). Key words: Balearic Islands, Ibiza, bird species, checklist, ecology Introduction Besides the millions of tourists who visit the Balearic Islands in every year, the four islands Menorca, Mallorca, Ibiza, and Formentera (the latter two also known as the Pityusic Islands) also attract many people interested in exploring their specific fauna and flora. Particular attention has been paid to the bird fauna inhabiting terrestrial, littoral, marine, and sometimes also fresh water areas. According to the review of V. JORDANS (1914, 1933), ornithological observations on the Balearic Islands have a long tradition and date back to the year 1653 when the first reports on the bird fauna 7 8 of Mallorca were published. Further classical avifaunistic explorations were conducted several times during the course of the 18th and 19th centuries for all the Balearic Islands. Modern overviews of Balearic avifauna have been provided by V. JORDANS (1914), MESTER (1971), BANNERMAN & BANNERMAN (1983), and CLAVELL I CORBERA (2002). The authors reviewed ornithological observations, even those providing data on the ecology of one single species, carried out during the 20th century. To date, 489 bird species are known to occur in Spain (without the Canary Islands), 436 of which are recorded to have flown over the province Catalunya (DE JUANA ET AL. 2000). 427 bird species have so far been recorded temporarily visiting or permanently living on the Balearic Islands, among them many exotic species (MAYOL 2003). Numerous bird species set off from their European breeding habitats and migrate towards African territories, where they spend the European winter period. Migrating birds on their way south which usually choose the western course over the Iberian peninsula and/or the short passage over the Western Mediterranean Sea, but are known to visit the Balearic Islands. The structure of pan-balearic bird migration has been well described by many authors, in specific studies as well as in general avifaunistic publications (e. g., GOETHE 1933, MOREAU 1953, MOREAU & MOREAU 1953, BLONDEL & VIELLIARD 1966, JENNING 1972, BAIRLEIN 1985). Since 1973, when the union of environmental research, or GOB1 (Grup Balear d´Ornitologia i Defensa de la Naturalesa) was founded, the number of ornithological observations has increased considerably. The GOB has also successfully initiated Balearic ornithological research in the fields of zoogeography, ecology and behaviour and critically evaluated incoming data. Since 1985, GOB activity has resulted in the publication of annual ornithological reports, Anuari Ornitològic de les Balears (e. g. REBASSA ET AL. 1998; GONZÁLEZ ET AL. 2000, 2002; RIERA et al. 2001; SUÁREZ ET AL. 2004, 2005; MARTÍNEZ ET AL. 2006). Most recently, two inventories of the avifauna of certain regions of Ibiza have been published: the “Parc Natural de Ses Salines”, including the salt flats (MARTÍNEZ 2003: 54 species recorded) and the northern part of the island, which is mostly free of anthropogenic influences (PALERM & CARDONA 2004). Although the established network of GOB-related ornithological activity has produced many useful data on the structure, diversity and dynamics of Balearic bird communities, we believe that there is still space for additional studies, especially because the density of avifaunistic observations for the four Balearic Islands is not always the same. Therefore, we set out to explore the avifauna of Ibiza in five field excursions and some additional experiments on the feeding ecology of certain resident species. The present paper provides a summary of these investigations and tries to contribute to a better understanding of habitat selection and temporal co- existence of breeding and migrating birds on Ibiza. Materials and methods Ornithological observations were carried out during five excursions to Ibiza in the years 1998-2001. Observations were made at different times of the year with the aim 1 http://www.gobmallorca.com 8 9 of covering the different succession stages within the bird community caused by transcontinental migrants. Very thorough studies were conducted during March and April 1999, 2000 and 2001. Additional data were obtained from excursions in the fall of the years 1998 (October) and 1999 (November), with reduced personnel, however. Birds were determined either visually with the aid of binoculars and/or by recording the song. Where possible, the number of bird species present in a given habitat was counted visually. With regard to the study area, the main focus of our bird watching activity was the north east of the island, and more precisely a triangle including the town and surroundings of Santa Eulària des Riu, the village Sant Carles de Peralta and the littoral areas of the north eastern coastline., We also checked other localities such as both parts of the salt flats (“regió grossa” and “regió petita”) in the south of Ibiza which are located between the airport and Puig des Falcó. Fig. 1. Map of the Pityusic Islands Ibiza and Formentera and their geographical position within the Western Mediterranean basin (red square in the left figure). The numbered circles inside the map indicate settlements and some bird watching sites. 1 – Sant Carles de Peralta 2 – Santa Eulària des Riu 3 – Eivissa 4 – Sant Antoni de Portmany 5 – Sta. Agnès de Corona 6 – Island of Tagomago 7 – Salt flats 8 – Island of Illa des Bosc. Efforts were made to include the main terrestrial and marine littoral habitats characterized by a specific geological profile and vegetation, including ruderal locations near villages, urbanisations or big towns, agricultural fields (with red soil, “terra rossa” and often lined by spacious brick walls), pinewood forests (dominated by Pinus halepensis and P. pinea), degraded bushy areas close to the coast (“Macchie”, “Garrigue”; e. g. juniper trees), waste disposal sites (near the Cala 9 10 Olivera), golf courses, sandy beaches, rocky shores (including the steep wall formations lining the coast of the north west of Ibiza), small islands situated in the vicinity of Ibiza’s coastline, and finally the open sea. Figure 1 provides an overview of all the major urbanisations and villages in Ibiza and, moreover, of all those areas visited for our ornithological observations. Results and discussion A total of 110 bird species were recorded for Ibiza while undertaking extensive ornithological observations in March/April 1998-2001 and October/November 1998- 1999, including both permanent residents and migratory birds. The species list with remarks on abundances, habitat preferences and status classification is given in the appendix. Our observations are not always congruent with the results obtained by two comprehensive studies by MARTÍNEZ (2003) and PALERM & CARDONA (2004). For instance, our list for those bird species inhabiting Ibiza’s salt flats lacks certain species more recently identified by MARTÍNEZ (2003), including residents such as the Water Rail (Rallus aquaticus) or the Pheasant (Phasianus colchicus). One reason for this incongruency is clearly the longer time span the authors mentioned had for